Title

Author

Date of Award:

1-1-1973

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

Gaylen L. Ashcroft

Abstract

Several large sources of 1ce nuclei were identified for the Wasatch Weather Modification Experimental Area. When stable air masses remained over the area for several days, ice nuclei concentrations as large as 1750 per liter (measured at -20 C) were found at the surface. ConcentralX tions as large as 6000 per liter were measured with an airborne 1ce nuclei counter over the smelter industry of the Salt Lake Valley. Ice nuclei concentrations during storm periods were usually less than 3 per liter, indicating an excellent potential for increasing precipitation amounts over the Wasatch Mountains through the release of artificial ice nuclei. Ice nuclei measurements taken during and following seeding activities indicate that nuclei are not being trapped in the Cache Valley and are not being funnelled into areas upwind of the seeding generators. The measure ments also indicated that nuclei are getting into the seeding area, at least at the ground level. Residual lee nuclei were found in the experimental area--an average oF 7.5 hours for ground seeders and 4.6 hours For airborne seeders--following seeding activities. Stability, wind direction, and cloud top temperatures were found to be the meteorological conditions most closely related to ice nuclei concentrations although this could not be shown through the use of statistical tests.